1. Technical Field
This invention applies to the field of fiber optics, and more particularly to a functional and protective apparatus that controls the distribution of light emitted from the end of a fiber optic light guide.
2. History of Related Art
Presently known optical light guides fall into the following categories; stranded glass, solio core glass, stranded polymer, solio core polymer and liquid core. Common factors of all presently known optical light guides are their reliance on uniformity of cross section perpendicularly of the points of termination to the central (axis of the light guide and cleanliness of the optical core at the points of termination. Distortion of the emitted light beam and resulting losses in light transmission efficiency and intensity will result if the aforementioned factors are not optimized at the time of installation and maintained throughout the life of the installation.
If area, task, decorative, or accent lighting are needed, it is usually desirable to introduce some form of optical beam control so that the emitted light serves the intended purpose. Examples of such efforts include U.S. Pat. Nos. 5,268,977; 5,303,125; and 5,486,984; all issued to Miller. U.S. Pat. No. 5,286,977 describes a fiber optic zoom-and-dim pin-spot luminaire with a complicated lens structure used to provide illumination with specific characteristics. However, the structure shown does not lend itself to quick disassembly favored by property owners, and further fails to protect the lens from the elements and associative dirt build-up which leads to reduced light transmission.
U.S. Pat. No. 5,303,125 speaks to a fiber optic amiable spotlight having a complex assembly structure which includes a bracketed mirror. This design is also rather difficult to assemble, and does not lend itself to use out of doors.
Finally, U.S. Pat. No. 5,486,984 discloses a parabolic fiber optic luminaire which leaves the ends of the fiber completely open to the elements. This design is also not suitable for use out of doors, and does not provide the desirable characteristics of an optically-guided beam.
The prior art also fails to address providing sufficient support to the fiber prior to its termination at the emitting end, so that the light beam exit point can be accurately predicted and angular excursion of the beam controlled. The failure to address this concern leads to fiber optic fixtures which produce irregular illumination patterns at a distance, distorted according to the deviation of the fiber centerline from the fixture centerline. For example, in a typical prior art fiber optic spotlight, a housing permits entry of a fiber by way of an entry tube. Light, which travels along the fiber centerline, exits the fiber end as fiber exit beams. A lens collimates the fiber exit beams to produce aligned lens exit beams. As long as the fiber centerline is perfectly aligned with the lens centerline, the fiber exit beams will be of equal length as they approach the lens on opposite sides of the lens centerline. Even illumination will then result. However, if the fiber is strained prior to passing through the entry tube, the fiber centerline will be nonparallel to the lens centerline and the illumination resulting from the fixture will be uneven. Further, if the strain is applied on a periodic basis, the illumination will also vary in accord with the amount and timing of the strain.
A prior art fiber optic lighting fixture which provides some relief from these problems has a housing that permits entry of the fiber by way of a four-part assembly, consisting of a support collar, a locking collar nut, a compression bushing, and a compression screw. Depending on the position of the fiber end within the support collar, and the position of support collar within the housing, the illumination provided by the fixture can be widened, narrowed, brightened, or dimmed. However, in some positions such as that required to produce a dimmed-wide beam of light from the fixture, the same off-axis problem described previously is present. That is, strain near the entry point of fiber into the compression screw may produce misalignment between the fiber centerline and the lens centerline. Depending on the direction of misalignment, either low lens exit beams or high lens exit beams will result.
The aforementioned fiber optic fixtures also provide no protection from the elements for the lens and fail to provide for the use of various effect elements (e.g. colored filters, honeycomb or linear louvers, linear lenses, diffusion lenses, etc.), which may be desired by the practical user to color the light, control glare, or vary the beam pattern. Further, the second fixture described requires a four-part assembly to affix the fiber to the housing for use. A less complex manner of attachment is desirable.
For the above and other reasons, it is therefore desirable to provide a fiber optic lighting fixture, suitable for task, area, or decorative lighting, which makes use of inexpensive lenses and various effect elements, is easily assembled and disassembled, is weather resistant so as to provide protection from the elements, and provides substantial support to the fiber inside the fixture so as to maintain alignment of the light beam, and provide even illumination. It is also desirable to provide a fixture which lends itself to inexpensive mass production. Further, it is desirable to have a lighting fixture which is modular, combining the foregoing qualities with choice of mounting devices to adapt the fixture to the required illumination application.